As a Californian, I find this so fascinating.I'm a yankee just slightly yooper-ised. Upper Peninsula Michigan are yoopers, I'm downstate lower peninsula, so still a yankee. I like being a yankee, it just sits quite right with me.
From wikipedia:
The term Yankee and its contracted form Yank have several interrelated meanings, all referring to people from the United States. Its various senses depend on the context, and may refer to New Englanders, residents of the Northern United States, or Americans in general. If you're intersted here is a link.
https://en.wikipedia.org/wiki/Yankee
For the record: I DO NOT want to know how everyone refers to Californians.